To prevail on a claim, you will need to establish negligence on the part of Fidelity and or/ its agent caused your loss. It isn't clear to me from your message whether you can in fact make out a claim for negligence, but it may be possible.
Since this is a securities matter, there is undoubtedly an arbitration provision in your contract documents with Fidelity and/or your agent, requiring that most claims be arbitrated before an agency whose acronym is FINRA. There may be an exception in the provision for claims that can be presented to a small claims court, and the small claims limit in CA now is $10K in some cases. You thus may be able to avoid arbitration by waiving any claim over $10K and going to small claims court -- but it will depend on the contract documents.
If you have questions, you should contact a lawyer who has experience in FINRA securities proceedings and negligence with respect to securities agents and brokers.
Good luck to you.